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Nitrate is difficult to form a precipitate due to its strong electronegativity, water solubility, making it difficult to be removed by rapid adsorption. Nitrate adsorption can be enhanced by increasing the positive charge of the adsorbent surface through chemical modification. The montmorillonite was modified with poly dimethyl diallyl ammonium chloride (PDADMAC), and PDADMAC was successfully loaded onto the surface of montmorillonite, and the adsorption mechanism was compared and analyzed by characterizing montmorillonite(Mt) before and after modification. The results show that: the content of quaternary amine nitrogen in modified montmorillonite (PDM-Mt) increases, and the surface potential increases significantly. The NO3--N adsorption capacity of PDM-Mt is 3.07 mg/g at pH=7, which is 86% higher than that before modification. The adsorption process is in accordance with the quasi-second-order kinetic model as well as the Langmuir adsorption isothermal model, that means it is mainly single-molecule layer chemisorption. The NO3--N adsorption process reaches equilibrium within 4 h, and the adsorption effect is obvious in the range of pH 5-7. After repeated 5 times, the adsorption capacity decreased by 21%, showing high recyclability. PDADMAC has the potential as a modifier to promote nitrate adsorption. [ABSTRACT FROM AUTHOR]

Polymer networks can have a range of desirable properties such as mechanical strength, wide compositional diversity between different materials, permanent porosity, convenient processability and broad solvent compatibility.sup.1,2. Designing polymer networks from the bottom up with new structural motifs and chemical compositions can be used to impart dynamic features such as malleability or self-healing, or to allow the material to respond to environmental stimuli.sup.3-8. However, many existing systems exhibit only one operational state that is defined by the material's composition and topology.sup.3-6; or their responsiveness may be irreversible.sup.7,9,10 and limited to a single network property.sup.11,12 (such as stiffness). Here we use cooperative self-assembly as a design principle to prepare a material that can be switched between two topological states. By using networks of polymer-linked metal-organic cages in which the cages change shape and size on irradiation, we can reversibly switch the network topology with ultraviolet or green light. This photoswitching produces coherent changes in several network properties at once, including branch functionality, junction fluctuations, defect tolerance, shear modulus, stress-relaxation behaviour and self-healing. Topology-switching materials could prove useful in fields such as soft robotics and photo-actuators as well as providing model systems for fundamental polymer physics studies.Using topology-switching metal-ligand cages to crosslink polymer networks produces gels whose chemical and mechanical properties can be radically and reversibly switched on irradiation., Author(s): Yuwei Gu [sup.1] , Eric A. Alt [sup.1] , Heng Wang [sup.2] , Xiaopeng Li [sup.2] , Adam P. Willard [sup.1] , Jeremiah A. Johnson [sup.1] Author Affiliations:(1) Department [...]

The research status and hotspots in the field of corneal cross linking (CXL) can benefit clinicians, researchers and the general public. The purpose of this study was to map the publishing trend on CXL research and explore the research hotspots. A bibliometric analysis was performed using the Web of Science Core Collection to investigate the publishing trend on CXL research. VOSviewer was used to build the knowledge map to visualise the number of annual publications, distribution of countries and institutions, international cooperation, author productivity, source journals and research hotspots in the field of CXL. A total of 2061 peer-reviewed articles on CXL research were collected from 2001 to 2020, and the annual research production increased over time. The United States was the country with the largest number of published articles, and the University of Zurich was the most active institution. Hafezi F published the largest number of articles on CXL, while Cornea was the journal with the largest number of studies on CXL. The most frequently cited references mainly focus on CXL in the treatment of keratoconus. The keywords were divided in 5 categories: 1) CXL mechanism, 2) ectasia diseases and refractive surgery, 3) corneal biomechanics, 4) efficacy evaluation, 5) treatment of infectious keratitis. The quantity and quality of articles on CXL were evaluated using bibliometric techniques by extracting the data from the Web of Science Core Collection. The research hotspots could provide insights on CXL research, providing valuable information for clinicians to perform research in this field and find potential partners. [ABSTRACT FROM AUTHOR]